JP2007192124A - Turbocharger - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To regulate flow speed of exhaust flowing from a nozzle to an inter-blade flow passage in a turbine wheel correctly to the optimum value during low rotation of an internal combustion engine, and restrict excessive pressure rise around the nozzle after the flow speed of the exhaust is set to the optimum value from middle to high rotation of the internal combustion engine. <P>SOLUTION: During low rotation of the internal combustion engine, inflow of exhaust to the inter-blade flow passage 16 in the turbine wheel 14 is carried out from a fixed nozzle 22 only. For the fixed nozzle 22, a fixed blade 24 is provided without a clearance to a nozzle wall surface, and gas flow area of the nozzle 22 is set at a proper value for low rotation of the internal combustion engine by the fixed blade 24. During middle to high rotation of the internal combustion engine, exhaust is sent from a variable nozzle 23 to the inter-blade flow passage 16, and a movable blade 24 of the variable nozzle 23 is displaced more on the opening side as engine rotation speed becomes higher. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a turbocharger used for supercharging an internal combustion engine.

  2. Description of the Related Art Conventionally, internal combustion engines for automobiles and the like are known in which a turbocharger is provided as a supercharger in order to improve output. Such a turbocharger includes a turbine scroll into which exhaust gas from an internal combustion engine is sent, a nozzle for flowing the exhaust gas in the turbine scroll through a passage between blades of the turbine wheel, and a compressor wheel that rotates integrally with the turbine wheel. Then, when the wheel rotates from the inflow of exhaust gas from the nozzle to the inter-blade flow path of the turbine wheel, the compressor wheel rotates accordingly and air is forcibly sent toward the combustion chamber of the internal combustion engine.

  By the way, when the internal combustion engine is running at a low speed, the exhaust flow rate of the engine is reduced, so that the flow rate of the exhaust gas flowing from the nozzle into the flow path between the blades of the turbine wheel decreases. Thus, when the flow velocity of the exhaust gas flowing into the inter-blade flow path of the turbine wheel decreases, the turbine wheel cannot be effectively rotated, and accordingly, the internal combustion engine can be effectively supercharged by the rotation of the compressor wheel. Disappear. In order to deal with these problems, when the internal combustion engine is running at a low speed where the exhaust flow rate is low, the flow rate of the exhaust gas flowing into the inter-blade passage of the turbine wheel is sufficiently high to effectively rotate the wheel. It is also conceivable to set the gas flow area of the nozzle small. However, when the gas flow area of the nozzle is set to be small as described above, the pressure in the vicinity of the nozzle becomes excessively high at the time of medium-high rotation of the internal combustion engine where the exhaust flow rate increases.

  Therefore, as shown in Patent Document 1, a nozzle with blades and a nozzle without blades are provided as the nozzle, and the gas flow area of the nozzle with blades is set to a value suitable for low rotation of the internal combustion engine. It has been proposed to provide a control valve that opens and closes in order to inhibit and permit the inflow of exhaust gas to the inter-blade flow path of the turbine wheel through it. In this case, when the internal combustion engine is running at a low speed, the control valve is closed and the inflow of exhaust gas to the inter-blade passage of the turbine wheel through the vaneless nozzle is prohibited. The inflow is performed only from the bladed nozzle. Therefore, when the internal combustion engine has a low rotational speed at which the exhaust gas flow rate is low, the flow velocity of the exhaust gas flowing into the inter-blade flow path of the turbine wheel can be sufficiently increased to effectively rotate the wheel. On the other hand, at the time of high rotation of the internal combustion engine, the control valve is opened to allow the inflow of exhaust gas to the inter-blade channel through the bladeless nozzle. For this reason, it is possible to suppress the pressure in the vicinity of the bladed nozzle from becoming excessively high during the high rotation of the internal combustion engine in which the exhaust gas flow rate increases.

  If the turbocharger of the above-mentioned patent document 1 is used, the flow rate of the exhaust gas flowing into the inter-blade passage of the turbine wheel when the internal combustion engine is rotating at a low speed and the suppression of the excessive pressure rise near the nozzle when the internal combustion engine is rotating at a high speed It becomes possible to improve the efficiency of supercharging by the turbocharger by achieving both. However, when the internal combustion engine is running at medium speed, the exhaust flow rate of the engine is about halfway between the low speed and the high speed, so the control valve is controlled to be either in the open state or the closed state. However, it is difficult to suppress the pressure in the vicinity of the nozzle from becoming too high while setting the flow velocity of the exhaust gas flowing into the inter-blade flow path of the turbine wheel to a value that effectively rotates the wheel. That is, when the control valve is opened during the middle rotation of the internal combustion engine, it is possible to suppress an excessive increase in pressure near the nozzle, but the flow velocity of the exhaust gas flowing into the inter-blade passage of the turbine wheel is the same as that of the wheel. Is less than the value that effectively rotates. Further, when the control valve is closed during the internal rotation of the internal combustion engine, the flow velocity of the exhaust gas flowing into the inter-blade passage of the turbine wheel can be increased to a suitable value, but the pressure near the nozzle is increased. It is inevitable that the supercharging efficiency will decrease due to excessive increase.

  In order to deal with these problems, instead of adopting the above-described configurations such as the nozzle with blades, the nozzle without blades, and the control valve, the nozzle may be provided with variable blades that open and close to make the gas flow area of the nozzle variable. Conceivable. FIG. 4 schematically shows the periphery of a turbine wheel of a turbocharger provided with such variable blades.

  As shown in the figure, the nozzle 104 for flowing the exhaust gas in the turbine scroll 101 to the inter-blade passage 103 of the turbine wheel 102 has a movable blade that opens and closes so that the gas flow area of the nozzle 104 is variable. 105 is provided. The opening / closing operation of the movable blade 105 is performed by the opening / closing mechanism 106. Here, the detailed structure of the opening / closing mechanism 106 will be described with reference to FIGS. 5 is a front view of the opening / closing mechanism 106 of FIG. 4 as viewed from the left side in the drawing, and FIG. 6 is a side sectional view of the opening / closing mechanism 106 of FIG. 5 as viewed from the direction of arrow AA.

  As shown in FIGS. 5 and 6, the opening / closing mechanism 106 includes a nozzle back plate 107 formed in a ring shape and a plurality of shafts 108 that can rotate through the plate 107 in the thickness direction. And. In the shaft 108, the movable wing 105 is fixed to one end thereof, and an opening / closing lever 109 is fixed to the other end thereof. An annular ring plate 110 is provided between the open / close lever 109 and the nozzle back plate 107 so as to overlap the plate 107 in the thickness direction. The ring plate 110 includes a pin 111 that is sandwiched between the bifurcated portions 109a of the open / close lever 109, and rotates in the circumferential direction based on driving of an actuator (not shown).

  Then, when the ring plate 110 is rotated about its circle center by driving the actuator, the pin 111 pushes the bifurcated portion 109 a of the opening / closing lever 109 in the rotation direction of the ring plate 110. As a result, the opening / closing lever 109 rotates the shaft 108, and as the shaft 108 rotates, the movable wings 105 open and close in a synchronized state around the shaft 108. Based on the opening / closing operation of the adjacent movable blades 105, the size of the gap between the movable blades 105, in other words, the gas flow area of the nozzle 104 changes.

As described above, in the turbocharger in which the variable vane is provided in the nozzle for flowing the exhaust gas in the turbine scroll to the flow path between the vanes of the turbine wheel, the gas flow area of the nozzle is changed by opening and closing the variable vane. Thus, the flow rate of the exhaust gas flowing through the nozzle and flowing into the inter-blade channel can be made variable. Therefore, when the internal combustion engine rotates at a low speed, the movable blade is displaced to the closed side, and as the rotational speed of the internal combustion engine increases, the variable blade is displaced to the open side to increase the gas flow area of the nozzle, It is considered that the following effects can be obtained. In other words, while adjusting the flow rate of the exhaust gas flowing into the inter-blade flow path to an optimal value at low engine speed, the pressure near the nozzle is adjusted to an optimal value at the exhaust gas flow rate from engine rotation to high rotation. It is considered possible to suppress a decrease in supercharging efficiency due to excessive increase.
JP-A-60-166718

  However, in a turbocharger in which variable vanes are provided on the nozzle, the flow velocity of the exhaust gas flowing from the nozzle to the flow path between the blades of the turbine wheel can always be adjusted to an optimum value when the internal combustion engine is running at a low speed where the exhaust flow rate is low. It was confirmed that it is not limited. This is presumed to be due to the following reasons [A] and [B].

  [A] In order to enable the opening and closing operation of the variable blades in the nozzle, a slight clearance is provided between the nozzle wall surface and the variable blades, and between the nozzles and the blades of the turbine wheel when the internal combustion engine rotates at a low speed. Even if the movable blade is displaced to the closed side in order to increase the flow rate of the exhaust gas flowing in the flow path, the flow rate of the exhaust gas is reduced by the amount of the exhaust leakage from the clearance. In addition, when the internal combustion engine is running at a low speed, since the exhaust flow rate of the internal combustion engine is small, the ratio of the amount of exhaust leaking from the clearance with respect to the entire exhaust flow rate becomes high, and the exhaust flow caused by the exhaust leak from the clearance is increased. The decrease in flow rate becomes significant. Therefore, at the time of low rotation of the internal combustion engine, it becomes difficult to increase the flow rate of the exhaust gas flowing from the nozzle to the inter-blade flow path of the turbine wheel to a value that can efficiently rotate the turbine wheel.

  [B] As shown in FIG. 7, there is a clearance between the bifurcated portion 109 a of the opening / closing lever 109 and the pin 111 of the ring plate 110. When the exhaust gas passes through the nozzle, an opening force F is applied to the movable wing 105, and this force F acts on the pin 111 in the direction of the arrow Y1 via the bifurcated portion 109a. The opening force F acting on the movable blade 105 when the exhaust gas passes through the nozzle becomes smaller as the movable blade 105 is displaced to the closed side.

  Here, when the internal combustion engine is rotated at a low speed and the movable blade 105 is displaced from the open side to the close side, the pin 111 pushes the bifurcated portion 109a in the direction of the arrow Y2 as the ring plate 110 is rotated by the actuator. Become. At this time, since the force F acts on the opening / closing lever 109, the upper side of the bifurcated portion 109a in FIG.

  However, after the movable blade 105 reaches the vicinity of the fully closed position, the pin 111 (ring plate 110) is displaced in the direction of arrow Y3 in FIG. 8 in order to displace the movable blade 105 to the open side as the rotational speed of the internal combustion engine increases. Since the force F is small, the bifurcated portion 109a cannot be displaced in the direction of the arrow Y3 by following the displacement of the pin 111. As a result, the pin 111 is first displaced relative to the bifurcated portion 109a relative to the bifurcated portion 109a relative to the bifurcated portion 109a in the direction of the arrow Y3. The opening / closing lever 109 is displaced in the opening direction.

  As the movable blade 105 is displaced to the opening side, the force F gradually increases, and even if the pin 111 is displaced in the direction of the arrow Y3, as shown in FIG. In any case, the bifurcated portion 109a is displaced relative to the pin 111 by the force F in the direction of the arrow Y1, and is pressed against the upper side of the pin 111 in the figure.

  FIG. 10 shows how the movable blade 105 is displaced in response to a change in the drive command value of the actuator during the above-described operation of the movable blade 105 at the time of low rotation of the internal combustion engine, such as the above-described opening → near fully closed → opening. It is a graph.

  As can be seen from the figure, when the movable blade 105 is displaced from the open state to the vicinity of the fully closed state, the movable blade 105 is fully moved as indicated by an arrow a in FIG. Displacement toward the closed position. Thereafter, when the actuator drive command value is changed to the open side to open the movable blade 105 near the fully closed position, the bifurcated portion 109a of the opening / closing lever 109 is changed from the state shown in FIG. 7 to the state shown in FIG. In the meantime, even when the drive command value is changed to the open side, the movable blade 105 is held near the fully closed position as shown by the arrow b in FIG. Subsequently, the movable blade 105 is displaced to the open side while the pin 111 and the bifurcated portion 109a are in the state shown in FIG. 8, and then the bifurcated portion 109a is moved to the state shown in FIG. Displace. At this time, as the actuator drive command value changes to the opening side, the movable blade 105 is displaced to the opening side as indicated by an arrow c in FIG.

  When the movable blade 105 is displaced from the vicinity of the fully closed position to the open side, even if the drive command value of the actuator is changed to the open side, the movable blade 105 is appropriately displaced (change in the direction opposite to the arrow a in FIG. 10). ) And is displaced only as indicated by arrows b and c. In the actuator drive region at the time of low rotation of the internal combustion engine indicated by the arrows b and c, the movable blade 105 is positioned closer to the closing side than the position (appropriate position) when the reverse change of the arrow a is indicated. There is a possibility that the flow velocity of the exhaust gas flowing through the nozzle and flowing between the blades of the turbine wheel becomes excessively high.

  For the reasons [A] and [B] described above, even if the nozzles are provided with variable vanes, the flow rate of the exhaust gas flowing from the nozzles to the inter-blade passages of the turbine wheel is reduced during low rotation of the internal combustion engine where the exhaust gas flow rate decreases. It becomes impossible to adjust to the optimum value.

  The present invention has been made in view of such circumstances, and its purpose is to accurately adjust the flow velocity of the exhaust gas flowing from the nozzle to the flow path between the blades of the turbine wheel at the time of low rotation of the internal combustion engine to an optimal value. It is to make it possible to suppress an excessive increase in pressure in the vicinity of the nozzle while setting the flow rate of the exhaust gas to an optimum value from the middle rotation to the high rotation of the internal combustion engine.

In the following, means for achieving the above object and its effects are described.
In order to achieve the above object, according to the first aspect of the present invention, there is provided a turbine scroll into which the exhaust gas of the internal combustion engine is sent, a nozzle for flowing the exhaust gas in the turbine scroll through the flow path between the blades of the turbine wheel, And a movable blade that opens and closes to change the gas flow area of the nozzle, and the nozzle rotates in the turbocharger that rotates by the inflow of exhaust gas from the nozzle to the flow path between the blades of the turbine wheel. In addition, a variable nozzle having the movable blade is provided, and a fixed nozzle is provided separately from the variable nozzle, and a fixed blade is provided in the fixed nozzle to set a gas flow area of the nozzle to a value suitable for low rotation of the internal combustion engine. When the internal combustion engine is running at a low speed, the valve is fully closed to prohibit the flow of exhaust gas into the variable nozzle. It was provided a control valve is fully opened to be allowed the flow of exhaust gas into the variable nozzle.

  According to the above configuration, exhaust flow into the variable nozzle is prohibited during low rotation of the internal combustion engine, and exhaust flow into the inter-blade passage of the turbine wheel is performed only from the fixed nozzle. The fixed nozzle is provided in a state where there is no clearance between the fixed blade and the nozzle wall surface, and the gas flow area of the nozzle is set to a value suitable for low rotation of the internal combustion engine by the fixed blade. Therefore, it is possible to accurately adjust the flow rate of the exhaust gas flowing from the fixed nozzle into the inter-blade passage of the turbine wheel when the internal combustion engine is rotating at a low speed to a value suitable for effectively rotating the turbine wheel. In addition, when the internal combustion engine rotates at a medium to high speed, the inflow of exhaust gas to the variable nozzle is permitted, and the gas flow area of the variable nozzle can be changed through the opening / closing operation of the movable blade. Therefore, when the internal combustion engine rotates at a medium to high speed, the flow velocity of the exhaust gas flowing into the inter-blade flow path is increased by displacing the movable blade to the open side and increasing the gas flow area of the variable nozzle as the rotational speed of the internal combustion engine increases. It is possible to suppress an excessive increase in pressure in the vicinity of the nozzle while adjusting the value to an optimal value.

Hereinafter, an embodiment embodying the present invention will be described with reference to FIGS.
FIG. 1 is a cross-sectional view showing a portion of an exhaust system side of a turbocharger 11 for supercharging an internal combustion engine mounted on an automobile.

  As shown in the figure, the turbocharger 11 includes a rotor shaft 13 that is rotatably supported by a center housing 12. A turbine wheel 14 is attached to one end portion (right end portion in the figure) of the rotor shaft 13. The turbine wheel 14 is provided with a plurality of blades 15 in a circumferential direction centering on the axis of the rotor shaft 13, and a space 16 between the blades 15 serves as a blade-to-blade channel 16.

  A turbine scroll 17 is attached to one end side of the center housing 12 so as to surround the outer periphery of the turbine wheel 14 and extend in a spiral shape. The inside of the turbine scroll 17 communicates with an exhaust passage 21 of the internal combustion engine, and exhaust gas of the internal combustion engine is sent from the exhaust passage 21. The exhaust gas fed into the turbine scroll 17 is caused to flow through the inter-blade channel 16 of the turbine wheel 14 so that the turbine wheel 14 and the rotor shaft 13 are rotated. When the rotor shaft 13 rotates, the compressor wheel attached to the other end of the shaft 13 also rotates, and accordingly, the air in the intake passage of the internal combustion engine is forcibly sent toward the combustion chamber.

Next, the internal structure of the turbine scroll 17 will be described in detail.
Inside the turbine scroll 17, two scroll passages 19 and 20 partitioned by a partition wall 18, that is, a scroll passage 19 positioned closer to the center housing 12 and a scroll passage 20 positioned away from the center housing 12 are formed. Has been. These scroll passages 19 and 20 are connected to an exhaust passage 21 of the internal combustion engine. A control valve 27 that is driven by an actuator 27a is provided at a connection portion between the scroll passage 20 and the exhaust passage 21. The control valve 27 opens and closes between a fully closed state and a fully opened state to prohibit / permit the inflow of exhaust gas from the exhaust passage 21 to the scroll passage 20 through driving by the actuator 27a.

  A fixed nozzle 22 is provided at a portion of the scroll passage 19 on the turbine wheel 14 side so that the exhaust in the passage 19 flows into the inter-blade passage 16 of the turbine wheel 14. A fixed blade 24 for setting a gas flow area of the nozzle 22 is fixed to the nozzle wall surface of the fixed nozzle 22. A plurality of fixed blades 24 are provided around the turbine wheel 14 at equal intervals in the circumferential direction as shown in FIG. With respect to the gas flow area of the fixed nozzle 22, the flow velocity of the exhaust gas flowing into the inter-blade passage 16 of the turbine wheel 14 from the scroll passage 19 through the fixed nozzle 22 when the internal combustion engine rotates at a low speed. Is set to a value that allows the wheel 14 to be effectively rotated.

  Further, a variable nozzle 23 is provided at the portion of the scroll passage 20 shown in FIG. 1 on the turbine wheel 14 side so that the exhaust gas in the passage 20 flows into the inter-blade passage 16. The variable nozzle 23 is provided with a movable blade 25 that opens and closes to make the gas flow area of the nozzle 23 variable. The movable blade 25 is opened and closed through an opening and closing mechanism 26 that is driven by an actuator 26a. A plurality of movable blades 25 are provided around the turbine wheel 14 at equal intervals in the circumferential direction as shown in FIG. When each movable blade 25 is opened / closed by the opening / closing mechanism 26 as indicated by the solid line and the broken line in the drawing, the size of the gap between the adjacent movable blades 25, in other words, the gas flow area of the variable nozzle 23 changes. It becomes like this.

  By the way, the supercharging efficiency of the turbocharger 11 is greatly influenced by the inflow mode of the exhaust gas into the inter-blade channel 16 such as the flow velocity when the exhaust gas flows into the inter-blade channel 16 of the turbine wheel 14. Further, the manner in which the exhaust flows into the inter-blade channel 16 of the turbine wheel 14 is variable through the opening and closing operations of the movable blade 25 and the control valve 27. Therefore, in order to effectively perform supercharging by the turbocharger 11, the movable blade 25 and the control valve 27 are set so that the exhaust flow into the inter-blade channel 16 is suitable for the operating state of the internal combustion engine. It becomes necessary to control.

  In this embodiment, the control of the movable blade 25 and the control valve 27 is performed through an electronic control unit 29 that performs various controls of the internal combustion engine mounted on the automobile. The electronic control device 29 inputs detection signals from various sensors such as a rotational speed sensor 28 that detects the rotational speed of the internal combustion engine, and opens and closes the movable blade 25 and the control valve 27 based on the engine operating state grasped from these detection signals. Drive control of the actuators 26a and 27a for operating is performed. Through such control of the movable blade 25 and the control valve 27, the manner in which the exhaust gas flows into the inter-blade passage 16 of the turbine wheel 14 is a mode suitable for realizing effective supercharging by the turbocharger 11.

Next, the control of the movable blade 25 and the control valve 27 will be described in detail.
When the internal combustion engine is running at a low speed, the control valve 27 is fully closed and the inflow of exhaust gas from the exhaust passage 21 to the scroll passage 20 is prohibited. Therefore, the inflow of exhaust gas from the scroll passage 20 to the variable nozzle 23 is also prohibited. The At this time, exhaust gas flows from the exhaust passage 21 to the scroll passage 19, and the exhaust gas in the scroll passage 19 flows through the fixed nozzle 22 to the inter-blade passage 16 to the turbine wheel 14. Therefore, when the internal combustion engine is rotating at a low speed, the inflow of exhaust gas into the inter-blade channel 16 of the turbine wheel 14 is performed only from the fixed nozzle 22. The fixed nozzle 22 is provided in a state where there is no clearance between the fixed blade 24 and the nozzle wall surface, and the gas flow area of the nozzle 22 is set to a value suitable for a low rotation of the internal combustion engine by the fixed blade 24. It is set to be. Therefore, the flow rate of the exhaust gas flowing from the fixed nozzle 22 to the inter-blade passage 16 of the turbine wheel 14 when the internal combustion engine rotates at a low speed can be adjusted to a value suitable for effectively rotating the turbine wheel 14.

  Further, when the internal combustion engine is rotating at a middle or high speed, the control valve 27 is fully opened, and the inflow of exhaust gas from the exhaust passage 21 to the scroll passage 20 is permitted. Allowed. For this reason, the exhaust gas flows into the inter-blade passage 16 of the turbine wheel 14 from both the fixed nozzle 22 and the variable nozzle 23 during middle and high speed rotation of the internal combustion engine. In the variable nozzle 23, the gas flow area is variable through the opening / closing operation of the movable blade 25. Such opening / closing operation of the movable blade 25 is performed according to the engine operating state such as the rotational speed of the internal combustion engine. Specifically, the movable blade 25 is displaced to the open side as the rotational speed of the internal combustion engine increases during medium to high rotation of the internal combustion engine. As a result, when the internal combustion engine rotates at a medium to high speed, the flow rate of the exhaust gas flowing from the variable nozzle 23 into the inter-blade passage 16 of the turbine wheel 14 is adjusted to an optimum value for effectively rotating the wheel 14. It is possible to prevent the supercharging efficiency of the turbocharger 11 from being reduced due to an excessive increase in pressure in the vicinity of the nozzle 23.

It should be noted that an arbitrary range from the fully closed position to the fully open position can be set as the movable range in the opening / closing direction of the movable blade 25 at the middle / high rotation speed of the internal combustion engine.
Here, if the movable range in the opening / closing direction of the movable blade 25 is set so that the movable blade 25 can be displaced near the fully closed position, when the movable blade 25 is displaced close to the fully closed position, the variable nozzle From the clearance between the nozzle wall surface and the movable blade 25 in FIG. However, since the exhaust flow rate from the engine is large at medium and high speeds of the internal combustion engine and the ratio of exhaust leakage from the clearance to the entire exhaust flow rate is low, this exhaust leakage flows into the inter-blade passage 16 of the turbine wheel 14. It does not affect the flow rate of exhaust gas.

  Further, as described above, when the movable range of the movable blade 25 is set in the opening / closing direction so that the movable blade 25 can be displaced near the fully closed position, the movable blade 25 is displaced toward the closed side to near the fully closed position. If the movable blades 25 are displaced to the open side after that, the problem described in [B] above occurs in which the movable blade 25 shifts to the closed side from the proper position. However, the gas flow area when the exhaust gas flows into the inter-blade flow path 16 of the turbine wheel 14 at this time is a large value obtained by adding the gas flow area of the variable nozzle 23 and the gas flow area of the fixed nozzle 22. For this reason, compared with the total value of these gas distribution areas, the reduction amount of the gas distribution area resulting from the shift | offset | difference of the closing side of the said movable blade 25 becomes a very small thing. Therefore, the reduction in the gas flow area caused by the shift of the movable blade 25 on the closed side does not affect the flow velocity of the exhaust gas flowing into the inter-blade channel 16 of the turbine wheel 14.

According to the embodiment described in detail above, the following effects can be obtained.
(1) When the internal combustion engine is running at a low speed, exhaust gas flows from only the fixed nozzle 22 to the inter-blade channel 16 of the turbine wheel 14 so that the flow velocity of the exhaust gas flowing into the inter-blade channel 16 effectively causes the turbine wheel 14 to flow. The value is suitable for rotation. Further, when the internal combustion engine is rotating at a medium to high speed, exhaust gas is also flowed from the variable nozzle 23 to the inter-blade channel 16, and the movable blade 25 of the variable nozzle 23 is displaced to the open side as the engine rotational speed increases. As a result, the pressure of the pressure in the vicinity of the variable nozzle 23 is adjusted while adjusting the flow velocity of the exhaust gas flowing from the variable nozzle 23 into the inter-blade channel 16 of the turbine wheel 14 to effectively rotate the wheel 14. It is possible to prevent the supercharging efficiency of the turbocharger 11 from being lowered due to excessive increase.

In addition, the said embodiment can also be changed as follows, for example.
The partition wall 18 in the turbine scroll 17 is abolished and only one scroll passage is formed in the turbine scroll 17, and a fixed nozzle 22 and a variable nozzle 23 are provided in a portion near the turbine wheel 14 in the one scroll passage. May be. In this case, a control valve that opens and closes between a fully closed state and a fully open state is provided on the variable nozzle 23 side in the scroll passage so as to prohibit / permit the inflow of exhaust gas from the passage to the variable nozzle 23.

  The movable range of the movable blade 25 in the opening / closing direction may be a range including the vicinity of the fully closed or a range not including the vicinity of the fully closed.

FIG. 3 is a cross-sectional view showing a portion on the exhaust system side of the internal combustion engine in the turbocharger of the present invention. Sectional drawing which shows the structure around the fixed nozzle in the turbine scroll of the said turbo jar. Sectional drawing which shows the structure around the variable nozzle in the turbine scroll of the said turbo jar. The schematic diagram which shows the conventional example around the turbine wheel of the turbo jar provided with the movable blade. The top view which shows the structure of the opening / closing mechanism for opening / closing a movable blade. Sectional drawing which looked at the opening / closing mechanism of FIG. 5 from the arrow AA direction. The enlarged view which shows the variable wing periphery in the said opening / closing mechanism. The enlarged view which shows the variable wing periphery in the said opening / closing mechanism. The enlarged view which shows the variable wing periphery in the said opening / closing mechanism. The graph which shows the displacement aspect of a movable blade with respect to the change of the drive command value of an actuator.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 11 ... Turbocharger, 12 ... Center housing, 13 ... Rotor shaft, 14 ... Turbine wheel, 15 ... Blade, 16 ... Flow path between blades, 17 ... Turbine scroll, 18 ... Partition wall, 19, 20 ... Scroll passage, 21 ... Exhaust passage, 22 ... fixed nozzle, 23 ... variable nozzle, 24 ... fixed blade, 25 ... movable blade, 26 ... opening / closing mechanism, 26a ... actuator, 27 ... control valve, 27a ... actuator, 28 ... rotational speed sensor, 29 ... electronic Control device.

Claims (1)

Turbine scroll to which the exhaust gas of the internal combustion engine is sent, a nozzle for flowing the exhaust in the turbine scroll to the flow path between the blades of the turbine wheel, and an opening / closing operation to change the gas flow area of the nozzle provided in the nozzle A turbocharger that rotates by the inflow of exhaust gas from the nozzle into the flow path between the blades of the turbine wheel,
A variable nozzle including the movable blade as the nozzle is provided and a fixed nozzle is provided separately from the variable nozzle,
The fixed nozzle is provided with fixed blades for setting the gas flow area of the nozzle to a value suitable for low rotation of the internal combustion engine,
A control valve which is fully closed to prohibit the inflow of exhaust gas to the variable nozzle when the internal combustion engine is running at a low speed, and is fully opened to permit the inflow of exhaust gas to the variable nozzle when the internal combustion engine is running at a medium or high speed. A turbocharger characterized in that it is provided.

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